This invention relates to an air vent for supplying outside air for combustion to a heater, and in particular to an air vent that automatically locks after air is no longer required to prevent the intrusion of cold air.
It is now recognized that with any heater generating heat through combustion, such as a furnace or fireplace, it is desirable to draw the combustion air from the outside, rather than using the already heated inside air. In addition to wasting heated air, using the internal air lowers the pressure inside the building causing the cold external air to be drawn inside through gaps around doors and windows.
Thus, numerous devices have been made to supply external combustion air to fireplaces or furnaces. For example, Bolinger, U.S. Pat. No. 2,409,731, discloses a fireplace having an air supply duct with a manually operated door. Dyer, U.S. Pat. No. 3,805,764, discloses a heating system with exterior air inlet for combustion chamber. The system includes a tube extending from the exterior of the building to the combustion chamber of the furnace. Wilhoite, U.S. Pat. No. 4,108,144, discloses a supplemental air supply for a fireplace. The device includes manifolds on either side of the fireplace opening to supply air to the fireplace through manually adjusted outlets. The manifolds are connected to pipes to provide outside air for combustion. Grott, U.S. Pat. No. 4,121,562, discloses an energy conservation kit for household furnaces. The kit includes an air duct for connecting the furnace to the exterior. The duct contains a flapper valve to insure that air only travels inwardly. Kellogg (deceased) et al., U.S. Pat. No. 4,195,618, discloses a fireplace venting system. The device comprises a plurality of holes about the periphery of the fireplace opening to supply combustion air. The holes are connected to a conduit or duct which is connected to an inlet. A damper is formed in each conduit to manually close it when the fireplace is not in use. Berg, U.S. Pat. No. 4,156,418, discloses an air intake system for an enclosed freestanding fireplace. The device has a conduit for the introduction of outside air into a closed fireplace. Bellaff, U.S. Pat. No. 4,285,325, discloses a balancing air device for a heating unit. The device comprises an air line for providing combustion air to a furnace. The air line has a bypass for venting excess air, and can be provided with a manually operated damper. Kogut, U.S. Pat. No. 4,498,624, discloses a control unit with separate dampers for make up and combustion air circulation. The control unit has two separate inlets, each inlet responsive to a pressure differential to operate both dampers.
With any combustion heater, and especially with fireplaces which usually open into the occupied rooms of a building, it is important to close the air supply after the fire is out to prevent cold outside air from entering. However, few of the prior art combustion air supply devices had any means to close the air supply, and those that did had to be manually operated. Often by the time the fire has died out, the users have left the room or would simply forget to close the air supply. The open air supply would allow cold air to infiltrate the room. What was needed was a simple, inexpensive device that could supply combustion air but which would automatically close and lock when the influx of combustion air was no longer needed.
Applicant has solved this need by providing an elegantly simple, inexpensive control device for a combustion air vent. The device is particularly well suited for fireplaces. The vent, a simple air duct, is preferably installed adjacent the fireplace hearth, near the floor, and extends through the wall to the exterior of the building. The exterior end of the conduit is preferably provided with a cowling to shield the opening. Various screens and/or filters can be provided over the inlet to block the passage of debris or small animals.
The outlet opening preferably also has a cowling to shield the opening and to channel the exiting air downwardly. Within this cowling, a cover is positioned over the outlet and hingedly secured at the top. Depending from the bottom of the cover is a tab of hook-and-loop type fastening material. Immediately below the outlet, in position to contact the tab on the cover, is a mating patch of hook-and-loop type fastening material.
The cover is weighted such that it is sufficiently light that the pressure differential caused by the combustion in the fireplace keeps the cover at least partially open so that air can be drawn in from the outside for combustion. However, the cover is sufficiently heavy so that when the fire dies and eliminates the pressure differential, the impact of the closing flap gate is sufficient to engage the tab and patch of mating hook-and-loop type fastening material to lock the cover in the closed position. The cover can also be manually locked in the closed position by position by pressing the tab and patch together. A second patch of hook-and-loop type fastening material can be provided on the inside of the cowling so that the cover can be locked in the open position.
When a fire is started, the cover is quickly and easily opened by pulling the tab on the cover free. The cover can either be locked in the open position or left unattached so that the pressure differential can maintain the cover at least partially open. When the fire dies down, the pressure differential diminishes and the cover falls shut, the impact locking the cover in the closed position.
The device of this invention is elegantly simple, inexpensive, and easy to install. It provides an easily controllable supply of combustion air for a fireplace or the like. The device automatically closes and locks when no more combustion air is needed. The device can also be manually locked in either the open or closed positions.